A while back I had an app up that done this exact same thing. Google took it down because it had a picture of duke nukem. Because there was a ton of people (I think in the 100,000 range) that loved the app.I brought it back.
I 100% made the sound, pic, and obviously the app. So there shouldn't be a problem.
While the app is free, if you want to help support me in making these apps. Check out the following. https://www.youtube.com/user/TechRHelp
Oh and if you or Google (I have a feeling Google will try to mess me over again) wants to check the code. https://github.com/crua9/Get-back-to-work-Android
NOTE: I made it where the app works even if the screen is off, and when you're in another app. You have to hold down your home button and swipe it to close it. I did this because I found people were getting a kick out of it telling people to get back to work when they were walking around at work or somewhere. (even more if they forgot they had it on)
Another thing to note is the shake sensitivity is up pretty high. If you want, you can go into github and change the code to make it more sensitive. (I made it like this because I didn't want the app to go off on the slightest motion)
I forgot to add the permissions so it works on all phones.